1. Field of the Invention
This invention relates generally to tire pressure warning devices and more particularly is directed towards a new and improved acoustical signal generating device for use with a pneumatic tire including improved cap seals and whistle construction as well as improved piston configuration.
2. Description of the Prior Art
In commonly assigned U.S. Pat. Nos. 3,489,998, 3,890,595 3,738,308, 4,031,845, 3,934,223, 4,103,282 and 4,186,377 there are disclosed tire pressure warning systems and components thereof adapted to monitor the air pressure in a pneumatic tire and to warn the operator in the event of abnormal tire pressure condition. In a typical embodiment of the system, an acoustical signal generating device is mounted on each wheel of a vehicle such as a passenger car and, in the event that the air pressure in any one or more of the tires drops below a predetermined limit, an acoustical signal is then picked up by a microphone mounted on the chassis of the vehicle. The microphone converts the acoustical signal to an electrical signal which is then processed, stored in memory if the vehicle is parked for overnight, for example, and then delivered to a warning device such as a light or alarm, typically on the dashboard of the car so that the driver will be alerted to the tire pressure condition.
It is an object of the present invention to provide improvements in the acoustical signal generating device mounted on each wheel. A more specific object of the invention is to provide an acoustical signal generating device which is unaffected by the centrifugal forces developed in the tire when the vehicle is in motion. A further object of this invention is to provide improved cap seals for use with acoustical tire pressure warning devices.